multiversion-concurrency-contro VS entt

https://github.com/samsquire/multiversion-concurrency-contro...

And I implemented a 3 way text diff with myers algorithm based on https://blog.jcoglan.com/2017/02/12/the-myers-diff-algorithm...

https://github.com/samsquire/text-diff

I implemented an eventually consistent mesh protocol that uses timestamps to provide last write wins

I think I lean towards per-thread sharding instead of mutex based or lock free data structures except for lockfree ringbuffers.

You can get embarassingly parallel performance if you split your data by thread and aggregate periodically.

If you need a consistent view of your entire set of data, that is slow path with sharding.

In my experiments with multithreaded software I simulate a bank where many bankaccounts are randomly withdrawn from and deposited to. https://github.com/samsquire/multiversion-concurrency-contro...

I get 700 million requests per second due to the sharding of money over accounts.

If you want some sample code to implement MVCC, I implemented MVCC in multithreaded Java as a toy example

https://github.com/samsquire/multiversion-concurrency-contro...

First read TransactionC.java then read MVCC.java

I wrote an unrolled switch statement in Java to simulate eager async/await across treads.

https://github.com/samsquire/multiversion-concurrency-contro...

The goal is that a compiler should generate this for you. This code is equivalent to the following:

   task1:

https://doc.rust-lang.org/book/ch16-00-concurrency.html

I've been working on implementing Java async/await state machine with switch statements and a scheduling loop. If the user doesn't await the async task handle, then the task's returnvalue is never handled. This is similar to the Go problem with the go statement.

https://github.com/samsquire/multiversion-concurrency-contro...

If your async call returns a handle and

yield value2++

https://github.com/samsquire/multiversion-concurrency-contro...

I am still working on allowing multiple coroutines to be in flight in parallel at the same time. At the moment the tasks share the same background thread.

I asked this stackoverflow question regarding C++ coroutines, as I wanted to use coroutines with a thread pool.

https://stackoverflow.com/questions/74520133/how-can-i-pass-...

This is very interesting. Thank you for submitting this and thank you for working on this.

I am highly interested in parallelism and high concurrency. I implemented multiversion concurrency control in Java.

https://github.com/samsquire/multiversion-concurrency-contro...

I am curious how to handle replication with high concurrency. I'm not sure how you detect dangerous reads+writes to the same key (tuples/fields) across different replica machines. In other words, multiple master.

I am aware Google uses truetime and some form of timestamp ordering and detection of interfering timestamps. But I'm not sure how to replicate that.

I began working on an algorithm to synchronize database records, do a sort, then a hash for each row where hash(row) = hash(previous_row.hash + row.data)

Then do a binary search on hashes matching/not matching. This is a synchronization algorithm I'm designing that requires minimal data transfer but multiple round trips.

The binary search would check the end of the data set for hash(replica_a.row[last]) == hash(replica_b.row[last]) then split the hash list in half and check the middle item, this shall tell you which row and which columns are different.

https://github.com/samsquire/multiversion-concurrency-contro...

I want to redesign the architecture of the async/await to be easier to understand. I want to use a state machine somehow.

I wrote an unrolled state machine for my async/await in Java. This models a simple async/await program and runs tasks on other threads - without locks. I use a design I call token ring parallelism, where threads take turns and are linked together in a ring structure.

https://github.com/samsquire/multiversion-concurrency-contro...

I wrote a own lock free algorithm here that I use to do message passing between actor threads. My goal is high throughput performance and low latency.

https://github.com/samsquire/multiversion-concurrency-contro...

With 11 threads (on a 12 core processor, deliberately left one core for Windows)

I then started writing a parser for a high level language and then code generation from the AST to the imaginary assembly. My interpreter is multithreaded and can send integers between interpreters. It is very early and doesn't do much.

Code is at https://github.com/samsquire/multiversion-concurrency-contro...

The high level language looks similar to Javascript except I tried to parse everything as an expression. I need to parse functions as expressions.

I was experimenting with Protothreads in C recently to try understand how it worked and I wrote a giant switch statement and a while loop in Java to simulate async/await. It would be interesting to do codegen for coroutines.

here's that giant switch statement and scheduler https://github.com/samsquire/multiversion-concurrency-contro...

One idea for a stackless design I had was to preallocate memory for each method call for a call to that function and avoid a stack altogether. This would allow coroutines between methods and avoid the function colour problem because everything is a coroutine.

Is there any communities for programming language developers? Where do all the language developers meet up and talk theory and implementation? I am on eatonphil's discord and we talk there.

One problem I am trying to understand how to solve is how you would write a multithreaded interpreter and language that allowed parallel interpretation similar to C# and Java. If the allocator is thread safe and you share an object pool between interpreters and you hash object equality by sourcecode, then you could send objects between threads with only a synchronization cost.

I believe Python has the problem that object identity is different in each subinterpreter so you need to marshall the data.

EnTT is a popular alternative to flecs for C++, which has different performance/memory characteristics.

https://pastebin.com/VPypiitk This is a very small experiment i did to learn the metaprogramming features. its an ECS library using the same model as entt (https://github.com/skypjack/entt). In 200 lines or so it does the equivalent of a few thousand lines of template heavy Cpp while compiling instantly and generating good debug code.

Some walkthrough:

Line 8 declares a SparseSet type as a fairly typical template. its just a struct with arrays of type T inside. Next lines implement getters/setters for this data structure

Line 46 Base_Registry things get interesting. This is a struct that holds a bunch of SparseSet of different types, and providers getters/setters for them by type. It uses code generation to do this. The initial #insert at the start of the class injects codegen that creates structure members from the type list the struct gets on its declaration. Note also how type-lists are a native structure in the lang, no need for variadics.

Line 99 i decide to do variadic style tail templates anyway for fun. I implement a function that takes a typelist and returns the tail, and the struct is created through recursion as one would do in cpp. Getters and setters for the View struct are also implemented through recursion

Line 143 has the for expansion. This is how you overload the for loop functionality to create custom iterators.

The rest of the code is just some basic test code that runs the thing.

Since we wanted a common game simulation that would be on both the server and the client we looked into a few libraries that would fit our ECS needs. It was decided we were going to write this common part of our game in C++, but rust was considered. C++ was a familiar language for us so naturally EnTT and flecs came up right away. I had used EnTT before, writing some small demo projects, so our choice was made based on familiarity. In order to integrate with Unity we created a small C interface to communicate between our simulation code and Unity’s C#. Here’s close to what it looked like. I removed some parts for brevity sake.

Are you sure you don't want to use a C++ package manager? Libtcod is on Vcpkg and with that setup you could add the fmt library or EnTT. fmt fixes C++'s string handling and EnTT fixes everything wrong with the entities of the previous tutorials.

There's also a performance question. While we can now use Blueprint nativization to convert Blueprints to C++ the result will be a fairly naive version, fast enough for most purposes but not if you're trying to push every bit of performance. This is where you're looking at making sure you're hitting things such as using the CPU cache as well as possible for an ECS system (Look at ENTT or Flecs if you want to see what they're about and why you'd want one), or a system needing to process massive amounts of data quickly such as the Voxel Plugin.

For a modern engine you’re probably best looking at Unity’s DOTS. You may also want to check out some of the different open source ECS libraries such as flecs and EnTT are two popular ones for C++, but there’s lots of them. Largely you’ll see lots of different approaches taken, all with their own pros and cons. Not all of them will be performant (some focus more on the design benefits) while others will be optimised for certain use cases. What you should prioritise will depend on your specific needs.

You can think of DynaMix as combining one of these libraries with an ECS like entt(https://github.com/skypjack/entt)